Entropy

Entropy, in the theory of heat, is a special property of the heat in a body. It measures that part of the energy in the body or system of bodies which cannot be converted into work, though it is not identical with the unavailable energy. In evee-y heat transfer from bodies at higher temperatures to bodies at lower, the available energy is diminished and the entropy increased. In all such transfers the entropy tends to a maximum. [Heat, Energy.]